general protection fault in rdma_accept

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
86f84779d8e92a690b2f281175ea06b884cb6fa4 (Tue Mar 6 20:41:30 2018 +0000)
Merge branch 'siginfo-linus' of
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.
user-space arch: i386

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kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 17350 Comm: syz-executor7 Not tainted 4.16.0-rc4+ #254
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:rdma_accept+0xd3/0xe10 drivers/infiniband/core/cma.c:3781
RSP: 0018:ffff8801a9b57790 EFLAGS: 00010203
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff841bb636
RDX: 000000000000007a RSI: ffffc9000191e000 RDI: 00000000000003d4
RBP: ffff8801a9b57868 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff88613380 R11: 0000000000000000 R12: 1ffff1003536aef4
R13: 0000000000000000 R14: 00000000000043c6 R15: ffff8801a9b57840
FS: 0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f77c3b40
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 000000009bc21000 CR3: 00000001adf52002 CR4: 00000000001606e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
ucma_accept+0x686/0x970 drivers/infiniband/core/ucma.c:1092
ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1627
__vfs_write+0xef/0x970 fs/read_write.c:480
vfs_write+0x189/0x510 fs/read_write.c:544
SYSC_write fs/read_write.c:589 [inline]
SyS_write+0xef/0x220 fs/read_write.c:581
do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fe8c99
RSP: 002b:00000000f77c309c EFLAGS: 00000286 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000014 RCX: 0000000020007100
RDX: 00000000fffffdc6 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Code: 84 c0 74 08 3c 03 0f 8e c3 0a 00 00 48 8d bb d4 03 00 00 48 b8 00 00
00 00 00 fc ff df 45 8b b6 d0 04 00 00 48 89 fa 48 c1 ea 03 <0f> b6 14 02
48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RIP: rdma_accept+0xd3/0xe10 drivers/infiniband/core/cma.c:3781 RSP:
ffff8801a9b57790
---[ end trace 6c6e93637e844d46 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.